Preparation of pale paint, varnish, and enamel vehicles



Patented Apr. 4, 1939 UNITED STATES PATENT OFFICE rnnrm'rion or PALE PAINT, vARNisii, AND ENAMEL vnn cms Harold C. Cheetham, Philadelphia, Pa., and William L. Evers, Woodbury, N. 1., assignors to The Resinous Products & Chemical Company,

Philadelphia, Pa.

No Drawing. Application March 6, 937,

Serial No. 129,379 I 10 Claims. '(01. 134-26) 5 enamels embodying drying or semi-drying oils,

the usualinitial operation is to subject the oil with or without additions of synthetic or natural resins or other modifying ingredients to a heat treatment or cooking during which the oil is at least partially polymerized and the resins, if added, dissolved. This process, commonly referred to as bodying, is well known to those familiar with paint and varnish technique. It is usually carried out in an open kettle, the escaping vapors assisting, to some extent, in excluding air, the presence of which darkens the oil. For the production of the lightest colored vehicles, for example, those to be used for white enamels, colorless clear varnishes, .etc., the varnish manufacturer selects the lightest colored oils and resins available but even with the palest of starting materials darkening during processing is seldom, if ever, avoided.

The object of this invention is to provide a way to overcome this darkening during processing and to obtain pale paint, varnish, and enamel vehicles. It is a further object to provide a way to eifect a bleaching during processing so that the vehicle is lighter in shade than the starting materials.

It has been found that the addition of very small amounts of an organic ester of phosphorous acid to the oil or resin or both prior to or at the beginning of the heat treatment substantially diminishes the formation of color. Depending on the amount and nature of the impurities present in the oil and resin used, additions of less than 2% by weight of the oil, gives color improvement of as much as 2 units on the Hellige varnish color scale. While larger amounts have little if any effect llpJn the kettle behavior of the varnish, they do not effect an increased bleaching in proportion to the amount used. The addition of excessive amounts should be avoided as they may act as plasticizers similar to the esters of phosphoric acid and soften the ultimate film. Excessive quantities also cause an undesirable lowering of the drying rate. Addition within the range of from 0.05 to 0.75% will usually produce the maximum bleacing but the invention does not preclude the addition of larger quantities, par-- ticularly where their plastifying eflect is not undesirable and a reduced rate of drying unobjectionable. It is preferable, however, to use only enough to accomplish the desired bleacing.

In carrying out the ir ention no change in the varnish makers technique is necessary. The esters of phosphorous acid may be added either to the resin by the resin manufacturer, thereby producing a resin which when cooked in oil diminishes darkening or it may be added to the oil, 5

"or it may be added to the mixture of resin and oil by the varnish maker. Storage of resin or oil to.which the addition has been made does not affect the capacity of the esters to perform their function for it has been found that even after long storage the treated resin or oil retains its property of cooking up to a paler vehicle than one not so treated.

Any of the organic esters of phosphorous acid may be 'used for the purpose. Among those found suitable are the following:

1. Triarylphosphites (ArO)aP, triphenyl phosphite, tricresyl phosphite. trioctylphenyl phosphite, trinaphthyl phosphite.

2. Triarylthiophosphites (ArShP- triphenylthiophosphite.

3. Nitro derivatives of triarylphosphites-tri- (nitrophenyl) phosphite.

4. Trialkyl phosphites (R0) 3P'trimethyl phosphite, triethyl phosphite, trioctyl phosphite, trilauryl phosphite.

5. Dlalkyl phosphites (R0) 2POHdimethyl and dibutyl phosphite.

6. Mono alkyl phosphites ROP(OH)2-monobutyl phosphite.

The aromatic phosphites are readily prepared from phosphorus trichloride and phenols, the aliphatic from phosphorus trichloride and alcohol in the presence of pyridine and ether or from phosphorus trichloride and sodium alcoholate. In these reactions some compounds represented by the formulae (R0) :PCI and (RO)PC12 are sometimes formed. While it is not necessary to use purified phosphites, it is desirable to hydrolyze these chlorides and thereby prevent the formation of hydrogen chloride in the reaction mixture. This is not necessary however, for these compounds are themselves effective in preserving light color.

The phosphorous esters of monohydroxy phenols and monohydrlc alcohols are preferred, particularly the esters of monohydric phenols, because of their ease of prepartion but esters of polyhydric compounds such as those of glycol, glycerine,

hydroquinone, etc. may also be used. The less volatile esters are also preferred because of their permanence in the varnish kettle. These esters will improve the color of varnishes made from any of the drying or semi-drying oils such as linseed oil, China-wood oil, Perilla oil,

soy bean oil, sardine oil, sunflower oil, hem-pseed oil, etc. either when used alone or in admixture with one another or with non-drying oils such as cottonseed oil, castor oil, and beef tallow oil. They may also be used with any of the varnish resins both natural and synthetic, such as the oil-soluble phenol-formaldehyde condensates either unmodified or modified with rosin or ester gum; alkyd resins made from dibasic acids such as phthalic, maleic, sebacic, etc. and polyhydric alcoholssuch as glycerine and glycol, also either unmodified or modified with drying, non-drying or semi-drying fatty oil acids or rosin, hydrocarbon resins such as those obtained by the polymerization of styrene, coumarone and indene, or with natural resins such as Congo, Kauri, copal, etc. The presence of a resin is not essential to the action of the phosphorous esters for they decrease color formation in the heat bodying of oils to which no resin has been added.

- The following examples are given to illustrate the invention, with the understanding that it is not confined to the particular compositions and details of processing selected.

Example 1.-450 parts'by weight of synthetic resin of the maleic-glycerine-rosin condensate type, 240 parts of Chinawood oil, 100 par-ts of body Q linseed, oil, and 0.4 part of triphenyl phosphite, are heated in a varnish kettle to 580 F. An additional 100 parts of linseed oil is added and the varnish is held for desired body at 500 F. When the desired body is reached, 70 parts of soy bean oil is added, the batch is cooled, and reduced with 870 parts of petroleum spirits. This varnish is a suitable vehicle for white baking finishes or tin decorating lacquers. The color is definitely better than when no phosphorus compound is used.

Example 2.-In the preparation of a phenol formaldehyde-ester gum modified type synthetic resin, 2 parts of tricresyl phosphite are added and mixed in for each 450 parts by weight of resin. This treated resin is made into a varnish by heating 450 parts with 600 parts of China-wood oil to 560 F., then adding 150 parts linseed oil and holding the temperature at 500 F. until the proper body is obtained, cooling to 420 F., and diluting 1300 parts of petroleum spirits. 0.5% lead (based on oil weight) and 0.03% cobalt in the form of oil-soluble metallic salts are added as driers. The resulting varnish is of general utility of the 4-hour drying type, and is of much better color than when made without phosphorous esters.

Example 3.130 parts by weight of Congo resin, 31 parts of linseed oil, and 2 parts of trioctylphenyl phosphite are heated to 580-600 R, then cooled to 550 F. and tested for solubility. The batch is alternately heated and cooled between 550 and 600 F. until a drop is clear on a glass plate. 48 parts of linseed oil is added and the batch heated again to 585 F. One part of sugar of lead and A; part of manganese acetate are added, the batch cooled and reduced with petroleum spirits. This vehicle may be used as a furniture varnish. Its color is improved through the use of the phosphite.

The reason for improved color obtained by the addition of phosphorous esters is not fully understood but is believed to be due to these compounds 1. In the preparation of paints, varnishes and enamels containing drying or semi-drying oils the' improvement which comprises having present in the batch during cooking, an organic ester of phosphorous acid.

2. In the preparation of paints, varnishes and enamels containing drying or semi-drying oils the improvement which comprises having present in the batch during cooking, a phosphorous acid ester of a member of the group consisting of monohydric phenols and monohydric alcohols.

3. In. the preparation of paints, varnishes and enamels containing drying or semi-drying oils the improvement which comprises-having present in the batch during cooking, an aromatic ester of phosphorous acid.

4. In the preparation of paints, varnishes and enamels containing drying or semi-drying oils the improvement which comprises having present in the batch during cooking, a triaryl phosphite.

5. In the preparation of paints, varnishes and enamels containing drying or semi-drying oils the improvement which comprises having present in the batch during cooking, triphenyl phos- Dhite.

6. In the preparation of paints, varnishes and enamels containing oil-soluble resins and drying or semi-drying oils the improvement which comprises having present in the batch during cooking, less than 2% of an organic ester of phosphorous acid.

7. In the preparation of paints, varnishes and enamels containing oil-soluble resins and drying or semi-drying oils the improvement which comprises having present in the batch during cooking, less than 2% of a phosphorous acid ester of a member of the group consisting of monohydric phenols and monohydric alcohols.

8. In the preparation of paints, varnishes and enamels containing oil-soluble resins and drying or semi-drying oils the improvement which comprises having present in the batch during cooking, from 0.05 to 0.75% of an aromatic ester of phosphorous acid.

9. In the preparation of paints, varnishes and enamels containing oil-soluble resins and drying or semi-drying oils the improvement which comprises having present in the batch during cooking, from 0.05 to 0.75% triaryl phosphite.

10. In the preparation of paints, varnishes and enamels containing oil-soluble resins and drying or semi-drying oils the improvement which comprises having present in the batch during cooking, from 0.05 to 0.75% triphenyl phosphite.

HAROLD C. CHEETHAM. WILLIAM L. EVERS. 

